100hPa极涡、南亚高压的变化及大气环流分布特征

THE VARIATIONS OF POLAR VORTEX AND SOUTH ASIA HIGH AND CHARACTERS OF NORTHERN ATMOSPHERE CIRCULATIONS AT 100HPA

利用NCEP/NCAR高度场资料进行计算,对冬、夏极涡与南亚高压面积进行Morlet小波变换,并对100hPa高度场进行EOF分解和长期趋势分析。结果表明:极涡、南亚高压具有相似的演变特征,这种相似特征在前期冬季极涡与南亚高压之间表现更为明显,体现了准5年尺度和准20年尺度的周期变化,在变化的位相上则相反。EOF分析表明,前期冬季高纬度地区与中低纬度地区的环流变化呈相反趋势,且第一模态的时间系数与前期冬季极涡的趋势一致,第一模态在一定程度上反映了前期冬季大气环流分布。夏季第一模态全场为负值,体现了夏季100hPa整体异常性;第二模态反映了副热带中低纬度大气环流与高纬度大气环流变化相反。从其长期变化趋势来看,冬季高纬度地区的高度场呈负趋势变化,副热带地区呈正趋势变化,夏季除我国华北部分地区为负趋势变化外,均为正趋势变化。极涡、南亚高压的这种年代际变化与100hPa高度场的长期线性趋势变化有关。

The NCEP/NCAR re-analysis data and wavelet transform are used to study Polar Vortex and South Asia High. At the same time, the EOF analysis and long-term variation means are used to analyze 100 hPa geopotential height in winter and summer. The results shows that Polar Vortex and SAH has similar periodic characters, both of which displaying 5-year and 20-year time scales, and the characters of precedent Winter Polar Vortex and SAH were especially similar to each other. But the trends of Polar Vortex and SAH are opposite. EOF analysis shows that the structure of the first mode and the second mode display differences between high latitudes and low latitudes in winter. Meanwhile, the trends of time coefficient of the first mode and precedent Winter Polar Vortex are consistent. To some extent, the structure of the first mode reflects the characters of the precedent winter atmosphere circulations. In summer, the first mode displays negatively at the entire 100 hPa geopotential height, and reflects abnormal characters generally. The second mode displays differences between high latitudes and low latitudes and reflects the variations of Polar Vortex circles in summer. It means that the abnormal changes of atmosphere circulation of the Northern Hemisphere have close relations with Polar Vortex and SAH. The long-term variations display negative trends in high latitudes but positive ones in subtropical anticyclonic regions in winter. Expect for north China, which displays negatively, other areas displays positively, in summer. Polar Vortex and South Asia High are related with the long-term variations of 100 hPa geopotential height. As it is known, Polar Vortex exists in every season, but South Asia High exits mainly in summer, and precedent Polar vortex can affect later atmosphere circulations. Therefore, it can provide some theories to forecast abnormal variations of SAH by studying the characters of Polar Vortex, especially precedent Polar Vortex.